Ants can be a major pest in the garden because they ‘farm’ aphids and scale – they safeguard them in their nests over winter, then bring them out in spring and carry them onto the new plant growth, then collect the honeydew that aphids and scale excrete as they feed off the plant’s sap.
To make matters worse, ants defend these pests from their natural predators, but ants are easily excluded from fruit trees by using horticultural glue bands around the trunks. Once ants are prevented from climbing trees, the unprotected aphids and scale are quickly eliminated by predators.
The activities of ants aren’t restricted to the garden though, they do have a habit of annoyingly invading kitchens in search of food, and bringing pest insects onto indoor plants too.
When ant populations become excessively large and invasive, they can be sensibly reduced with the use of ant baits which have a low environmental impact.
How to Make Borax Ant Bait
The best way to reduce ant numbers is to use a bait which is toxic to them but doesn’t kill them instantly, so they can take it back to their nest and feed the rest of the ants there, slowly destroying the whole colony.
What is Borax?
Borax is a natural occurring mineral salt, sodium tetraborate decahydrate, and is commonly used as a laundry detergent booster and a multi-purpose cleaner. Like other laundry products, it’s poisonous when swallowed, so be sure to keep out of reach of children and pets.
When insects ingest borax, it acts as a stomach poison. The exact mode of action is not yet understood, but when borate salts dissolve inside an insect body they form boric acid. After ingestion, insects reduce their feeding, dry out and are eventually killed.
Borax Ant Bait Recipe
The following materials are required to make borax-based ant bait insecticide:
- 1/2 cup (approx. 140ml) of sugar
- 2 teaspoons of borax
- 350ml (12 oz) of water
To make the ant bait, follow the steps below:
- Pour 1/2 cup of sugar, 2 level teaspoons of borax and 350ml (12 ounces) of water into a glass jar or plastic bottle. Use a funnel if the bottle has a narrow mouth.
- Put the lid on the jar or bottle and tighten it firmly.
- Shake thoroughly until all the crystals are dissolved, this is the finished bait solution.
To mix up bigger batches of the borax ant bait, just double the quantities of ingredients, combine 1 cup of sugar, 4 level teaspoons of borax and 700ml (24 ounces) of water. That much ant bait should last quite a while, and stores well in a cool, dark place such as a laundry or kitchen cupboard.
How to Make an Ant Trap to Use With the Borax Ant Bait
The following materials are required to make an ant trap to use with the borax-based ant bait insecticide:
- glass jar or plastic bottle with lid (to mix the ingredients in)
- small jar with a lid (to use as the trap containing the bait)
- cotton wool balls
To construct the ant bait trap for indoor use, follow the instructions below:
- Place the cotton wool balls into the smaller jar and fill to half the height of the cotton wool with the bait solution. The cotton wool balls need to extend above the surface of the liquid so the ants can walk across the top of them to reach the bait solution.
- Make a few small holes in the centre of the lid of the small jar using an awl punch, drill or other suitable tool.
- Firmly screw the lid back onto the small jar, , this is the finished baited trap.
- Put trap near the entrance of the nest, or wherever ants have made a path into the house.
With this indoor ant trap, the holes for the ants to enter through are located at the top of the container. This isn’t suitable for outdoor use as the container will fill with water if left out in the rain.
It’s also possible to use the indoor trap outside by making a simple rain cover for it from a plastic bottle, as shown below.
How to Use the Indoor Ant Bait Trap in the Garden
When baiting ants outdoors, the trap needs to be protected from rain, otherwise it will flood and overflow, diluting the mixture and ruining it.
A simple rain cover that fits over the ant bait trap can be made from an empty soft drink bottle.
To make this ant bait trap rain cover:
- Get a soft drink bottle that is wide than the jar used for the trap.
- Cut off the top section of a soft drink bottle, allowing enough height so that the lid of the jar will not rest against the inside of the bottle.
- Cut out small doors along the bottom edge of the top section of soft drink bottle to allow the ants to enter through to reach the trap, make them large enough for unobstructed easy entry on uneven ground.
- Leave the cap on the top section of soft drink bottle to prevent any rain getting in.
Once the rain cover is placed over the ant bait trap jar, it should stay in place on its own, but if strong winds are blowing the cover off, a rock or other heavy object can be placed on either side to secure it better.
In very hot weather, the water may evaporate from the bait solution in the trap. To get around this problem, mark the water level on the side of the jar, and when it evaporates, top up with some plain water. Be aware that as the ants consume the liquid, its level will reduce, so don’t top up the water level if ants are coming, top up with more bait solution instead!
For a more permanent outdoor solution to ant problems, I’ve designed an ant trap specifically for outdoor use, made out of a plastic take-away food container that isn’t affected by rain for outdoor use in the garden, and to protect fruit trees, as pictured below. It also works indoors perfectly well too!
Further instructions for making the outdoor ant bait trap can be found in the article – How to Build a DIY Outdoor Ant Trap to Protect the Garden and Fruit Trees
Adjusting the Ant Bait Trap Mixture
The key is that the ants will get into the jar to eat the sugar and return to the nest and pass it on to the rest of the colony.
If many dead ants are found beside the jar, then the mixture is too strong, so dilute the solution by adding more sugar and water, or make a new batch with less borax and try again.
Some recipes specify using 2 tablespoons of borax rather than 2 teaspoons, which is three times as much (1 tablespoon = 3 teaspoons). Even using the amount in this recipe, I found some dead ants around the jar on the second day, so I suspect it’s strong enough. If the mix contains far too much borax, the ants will reject it and refuse to eat the bait.
With a proper mixture the colony may be destroyed in a few weeks, though it does take the destruction of the queen to completely eradicate a colony.
Ants Can Be Pests, But They’re Also Ecologically Beneficial
Though it may be sometimes necessary to control ant populations in the garden, or remove ants from the home, the goal is never to completely eradicate them from the garden, because they’re beneficial insects.
Here is a range of ecologically beneficial functions carried out by ants:
- Ants are predators and eat many pest insects, which helps keep pest populations down.
- Ants move roughly the same amount of soil as earthworms do, loosening the soil, and improving air and water movement through it.
- Ants keep the ecosystem clean by moving dead insects, plant and animal matter into their nests, fertilising the soil in the process.
- Ants carry seeds from one location to another, which help plants spread into new areas where they may survive and thrive much better.
It’s important to keep in mind that natural ecosystems are in a state of balance, and when dealing with garden pests, we should only do just enough to address the problem, and no more than that. A heavy-handed approach, such as spraying with toxic synthetic pesticides, always throws nature out of balance, needlessly killing off the more vulnerable beneficial predator insects and causing population explosions of pest insects.
For more information on ant control, see article – How to Make an Outdoor Ant Trap to Protect Fruit Trees from Aphid and Scale Pests
More articles on Garden Pests, Diseases and Problems
- Iowa State University, Extension and Outreach, Horticulture and Home Pest News – Ants Are Ecologically Beneficial, In Defense of Ants, 2020